The present application relates to devices, systems and methods related to edge-based communication with a plurality of slave devices.
For communication between devices, for example in automotive applications, various protocols are used. One protocol frequently employed is the SENT protocol (single edge nibble transmission). This protocol may for example be used in applications where high resolution data is transmitted for example from a sensor device to an electronic control unit (ECU).
The SPC protocol (short PWM code; PWM meaning pulse width modulation) is an extension of the SENT protocol and aims at increasing performance of a communication link and reducing system costs at the same time. To some extent, SPC allows bidirectional communication and is an example of an edge based PWM protocol. For example, SPC may introduce a half-duplex synchronous communication. A receiver (e.g. master) generates for example a master trigger pulse on a communication line by pulling it low for a defined amount of time. The pulse width (corresponding to the defined amount of time) is measured by a transmitter (e.g. slave), for example a sensor, and a transmission, e.g. a SENT transmission, is initiated only if the pulse width is within a defined limit. The SPC protocol allows choosing between various protocol modes. For example, a synchronous mode, a synchronous mode with range selection or a synchronous transmission with ID selection (also referred to as busmode), where up to four sensors may be connected in parallel to an ECU, may be used. In the latter case, the pulse width of the above-mentioned trigger pulse may define which sensor or other entity will start a transmission. For example, a length of the trigger pulse may indicate an ID of a sensor or other slave device selected for transmission. The sensor or other entity may start the transmission with its own synchronization, which may overlap the trigger pulse.
Conventionally, when using the SPC protocol in the above-mentioned busmode, each sensor may have a different length of the trigger pulse associated therewith. In the conventional SPC protocol, triggering a sensor by a trigger pulse has a comparatively long duration (for example about 90 time units for addressing, e.g. the trigger pulse and at least about 281 time units for responding of the sensor) and therefore takes a comparatively long time. Moreover, between triggering different bus participants like sensors in conventional approaches a pause has been made as the length of transmission from sensor to controller may depend on the data content of the transmission. Therefore, between triggering of different sensors in some conventional approaches at least the longest possible transmission duration plus a safety margin has been kept.
In conventional approaches, when for example a sensor receives a trigger pulse, this triggering causes the sensor to capture or sample sensor data and subsequently send it to a controller or other device. When reading out several sensors, this leads to the data of the different sensors being captured at different points in time, which for some applications may be undesirable.